The '''National Institutes of Health''' ('''NIH''') is the primary agency of the United States government responsible for biomedical
and public health
research, founded in the late 1870s. It is part of the United States Department of Health and Human Services
with facilities mainly located in Bethesda, Maryland
. It conducts its own scientific research through its NIH Intramural Research Program|Intramural Research Program
(IRP) and provides major biomedical research funding to non-NIH research facilities through its Extramural Research Program.
, the IRP had 1,200 principal investigator
s and more than 4,000 postdoctoral
fellows in basic, translational, and clinical research, being the largest biomedical research institution in the world,
while, as of 2003, the extramural arm provided 28% of biomedical research funding spent annually in the U.S., or about US$26.4 billion.